Gopher poison depositing tool

ABSTRACT

A gopher poison depositing tool having an elongated barrel with a reduced diameter at lower end portion, a receptacle for a cartridge of poison and opening the cartridge as it is inserted, a combination receptacle mounting and poison metering member mounted on the barrel to mount the cartridge exterior of the barrel and extend within the barrel, a plunger extending within the barrel, said plunger having an intermediate portion cooperating with the metering part of said combination member for dispensing a metered dose of poison upon retracting the plunger from a datum position to a retracted position whereby the metered dose falls to the lower end portion of the barrel, a lower plug that cooperates with the lower end portion of the barrel to block the discharge of poison therethrough when the plunger is in the datum position and permit the discharge of poison upon the plunger being retracted, and a handle portion exterior of the barrel, a guide member mounted on the upper end portion of the barrel for mounting the plunger on the barrel for reciprocal movement between its positions, a spring member acting against the plunger and the guide member for resiliently urging the plunger to its datum position, and a lock member on the handle for releasably retaining the plunger in its datum position.

United States Patent [191 Elston [4 1 Nov. 13, 1973 GOPHER POISON DEPOSITING TOOL [75] Inventor: Rue Raymond Elston, Hudson, Wis.

[73] Assignee: Rue R. Elston C0,, Inc.,

Minneapolis, Minn.

22 Filed: Apr. 17,1972

21 Appl. No.: 244,669

[52] 11.8. C1. 111/96 [51] Int. Cl A01n 23/00 [58] Field of Search 222/384, 457, 383,

Primary Examiner-Robert B. Reeves Assistant Examiner--Norman L. Stack, Jr. AttorneyRalph L. Dugger et a1.

[57] ABSTRACT A gopher poison depositing tool having an elongated barrel with a reduced diameter at lower end portion, a receptacle for a cartridge of poison and opening the cartridge as it is inserted, a combination receptacle mounting and poison metering member mounted on the barrel to mount the cartridge exterior of the barrel and extend within the barrel, a plunger extending within the barrel, said plunger having an intermediate portion cooperating with the metering part of said combination member for dispensing a metered dose of poison upon retracting the plunger from a datum position to a retracted position whereby the metered dose falls to the lower end portion of the barrel, a lower plug that cooperates with the lower end portion of the barrel to block the discharge of poison therethrough when the plunger is in the datum position and permit the discharge of poison upon the plunger being retracted, and a handle portion exterior of the barrel, a guide member mounted on the upper end portion of the barrel for mounting the plunger on the barrel for reciprocal movement between its positions, a spring member acting against the plunger and the guide member for resiliently urging the plunger to its datum position, and a lock member on the handle for releasably retaining the plunger in its datum position.

GOPHER POISON DEPOSITING TOOL BACKGROUND OF THE INVENTION A gopher poison depositing tool that is manually operated for depositing poison in a gopher runway.

In prior art manually operated gopher poison depositing tools there is a tendency for the lower end of the barrel to become plugged in use, or not discharge a properly metered quantity of poison. For example in U. S. Pat. No. 1,890,391, when the conical plug is moved to a discharge position, soil can collect on the plug shoulder adjacent the barrel and prevent the plug being moved to a fully retracted position. Further, when the level of poison in the upper chamber. is low, a desired dose will not be discharged. Additionally, if the conical plug is moved downwardly relatively slow, poison can drain from the upper chamber to the lower chamber and thus a different quantity of poison will be discharged than it the pointed plug were moved down faster. In order to overcome problems such as the above as well as others, this invention'has been made.

SUMMARY OF THE INVENTION A manually operated gopher poison depositing tool having an elongated barrel with a reduced diameter lower end portion, a plunger mounted on the barrel and extended thereinto for slidable movement between a datum position and a retracted position, the plunger having a plug for blocking the discharge of poison from the barrel when the plunger is in a datum position and permitting the discharge when in a retracted position, a metering chamber member extending within the barrel in substantial axial spaced relationship to the lower end portion to, in cooperation with metering parts of the plunger, discharge a metered dose of poison to fall to the barrel lower end portion upon the plunger being moved from its datum position to its retracted position.

One of the objects of this invention is to provide a new and novel gopher poison depositing to'ol having a plunger plug portion for blocking the discharge of poison from the barrel and prevent dirt moving into the barrel as the tool is inserted in the ground with the plunger in its datum position, and a metering member cooperating with the plunger at a substantially spaced location from the plug to dispense a measured does of poison to fall through the barrel as the plug is moved from the plunger datum position to the plunger retracted position.

Another object of this ivne ntion is to provide a new and novel gopher poison depositing tool having a receptacle for poison exterior of the barrel of the tool and a metering portion cooperating with the plunger for dispensing a metered dose of poison as the plunger is moved from a datum position preventing dirt moving into the barrel as the barrel is inserted into the ground, and permit the discharge of poison as the plunger is retracted relative to the barrel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of the apparatus of this invention with the tool extended into a gopher runway and the plunger in its datum position, the handle being shown 90 relative its normal angular position relative the barrel for convenience of illustration;

FIG. 2 is a somewhat enlarged view of the structure of FIG. 1 other than that portions are broken away and the plunger is shown in its retracted position;

FIG. 3 is an enlarged transverse cross-sectional view generally taken along the line and in the direction of the arrows 33 of FIG. 1 to more clearly illustrate parts of the metering portion of the tool;

FIG. 4 is a transverse cross-sectional view generally taken along the line and in the direction of the arrows 44 of FIG. 1 to illustrate parts of the metering portion of the tool; and

FIG. 5 is an enlarged transverse cross-sectional view generally taken along the line and in the direction of the arrows 5-5 of FIG. 1 to illustrate the mechanism for blocking rotational movement of the plunger relative to the barrel while permitting the plunger being moved from its datum to its retracted position.

Referring to the drawings, the gopher poison depositing tool, generally designated at 10, includes an axially elongated barrel 11 having an elongated top cylindrical tubular portion 11A, an intermediate frusto conical tubular portion 11B having its major base end portion integrally joined to the lower end of portion 11A, a reduced diameter cylindrical tubular portion 11C having its upper end integrally joined to the lower end of portion 113, and a frusto-conical lower end portion 11D having its major base end integrally joined to the lower end of portion 1 1C. The lower terminal edge 11E of the barrel is of a smaller diameter than any other portion of the barrel while the axial length of reduced diameter 11C is greater than the normal depth of a gopher runway below ground level.

Slidably extended within the barrel is a plunger, generally designated 12. The plunger includes a plug 13 having a cylindrical portion 13A of an outer diameter to form a close fit with the inner periphery of edge 1 1E, a lower conical point 133, and an upper frusto-conical portion that is joined to the lower end of an elongated rod portion 14. Rod portion 14 is of a substantially smaller diameter than the diameter of plug portion 13A and of the inner diameter of barrel portion 11C, and of an axial length greater than the axial length of barrel portion 11C.

The upper end of rod 14 is joined to the lower end of a plunger lower meter member 15 that has a cylindrical outer surface of a substantial greater diameter than rod 14 but of a smaller diameter than the diameter of the part of the tapered barrel portion 118 that it is radially adjacent thereto when the plunger is in its datum position. The upper end of meter member 15 is joined to the lower end of rod 16 of the plunger, the rod 16 being of a substantially smaller diameter than the diameter of meter member 15. Preferably at least the major portion of the top surface 15A of member 15 that extends transversely outwardly of the rod 16 is inclined at a steep angle relative the axis of the elongation of the barrel for purposes to be set forth hereinafter.

The upper end of rod 16 is joined to the lower end of the top cylindrical meter member 17 of the plunger while the lower end of a rod 18 is joined to member 17 to extend thereabove. The upper portion of rod 18 is slidably extended through a mounting member 19 which in turn is secured to the upper end portion of the barrel, for example by screws. The plunger handle 20 is mounted on the upper end portion of the rod 18 and is adjustable a limited axial amount relative thereto mounting member 19, and the plunger is in its datum position, the lower part of the plug cylinder 13A is radially opposite the barrel terminal edge MB. In order to resiliently retain the plungerin its datum position, an annular member 24 is mounted on rod 18 intermediate the top metering member 17 and the handle, a coil spring 25 being provided on rod 18 to have one end bear against annular member 24 and the opposite end against mounting member 19. For retaining the annular member 24 and thereby the plunger in a given angular position relative the barrel, the annular member 24 is provided with'an outer peripheral recess 26 of a shape to form a close sliding fit with the axially elongated, inwardly extending depression 27 formed in the barrel. The depression is of a sufficient axial length to extend into the cutout 26 in both the plunger datum position and the plunger retracted position. Even though the tool operates satisfactory with the handle in the angular relationship relative the barrel shown in FIGS. 1 and 2, it is preferred the handle extend relative the barrel at 90 (plunger rotated 90) from that shown whereby the receptacle 46 would be on the opposite side of the barrel from the user when the handle is grasped by both hands in the normal position of use.

A combination cartridge mounting and metering member, generally designated 30, includes an upwardly opening cup 31, and a chute 32 that is enclosed other than for the one end which opens to the bottom of the cup and an opposite end that is joined to a generally cylindrical tubular metering member 33 to open thereinto intermediate the opposite axial ends of metering member 33. The metering member 33 is of an axial length that is substantially greater than the maximum axial spacing between the bottom surface of member 17 and the top surface of member 15, the internal diameter of member 33 being such to form a close slidabe fit with the outer cylindrical surfaces of member 15, 17. A closure member 34 is joined to the chute to extend therearound intermediate the cup and meter member 33, the inner peripheral wall of the closure member being curved about the central axis of the meter member. The axial length and arcuate width of the closure member are greater than the corresponding dimensions of the cutout 37 that is formed in the barrel to open transversely adjacent the lower portion of member 17 and the upper portion of member when the plunger is in its datum position. The closure 34 is secured, for example, by screws to the edge portions of the barrel defining the cutout. The cutout is of sufficient size that the meter member 32 may be inserted into the barrel. As may be noted in FIGS. I and 2, when the closure member is mounted on the barrel, the chute is inclined at a relatively steep angle in an upwardly and radially outward direction relative the central axis of the barrel, and the top edge portion of the chute (bottom of the cup) is at a higher elevation than tubular member 33. Further, as may be more clearly seen in FIG. 4, there is a substantial structure free clearance space radially between the tubular member 33 and the inner peripheral wall of barrel portion lllA extending from the top of the tubular member to the bottom thereof, other than for the space occupied by the chute extending into the barrel. The before mentioned structural free space is sufficiently great to freely permit poison passing from the upper edge of the tubular member through the clearance space between the tubular member and barrel and to the lower edge of the tubular member.

Advantageously member 30 may be provided with generally sloping wall portions 38 that extend radially between the closure member and tubular member 32 from the upper half of the to the top of the tubular member 33, said wall portions having opposite surfaces sloped downwardly in diverging relation to one another to permit the chance gravity flow of poison over the surfaces. Thus the change of poison lodging on the top surface of the cute is minimized.

The tubular receptacle portion 42 of the poison container is open at each axial end and has its lower edge portion secured to the cup 31 to open thereinto and has a threaded upper end portion to which a cover 43 is threaded. Mounted by the cup to extend within the receptacle portion 42 is an opener 45, the opener puncturing a hole in the cartridge 46 as its inserted in the container and forced downwardly into the cup portion whereby the poison in the container will flow under gravity downwardly into the chute 32.

A lock lever 49 is pivotally connected to the handle at 50 and has a lower leg 49a extendable into the annular groove 51 of the mounting member 19. A spring member 52 is mounted by the handle in a position to bear against the lock lever for resiliently urging the lock lever to pivot about the pivot axis of pivot member 50 in the direction of the arrow 53 to a position to be extendable into the groove 51. The upper surface 19A of member 19 slopes downwardly radially outwardly of the rod 18 whereby when the lower leg 49A of the lever is above member 19 and the plunger is moved from its retracted position to its datum position, leg 49A as it moves over surface 19A is cammed outwardly against the resilient action of spring 52 and then snaps into groove Sll upon the plunger being moved to its datum position for releasably retaining the plunger in its datum position.

When using the apparatus of this invention, the cartridge of poison 46 is inserted in the receptacle whereby a hole is punctured inthe bottom thereof by the opener and the poison drains from the cartridge down into the chute 32. However, it is to be understood the poison may be poured directly into the receptacle formed by receptacle portion 42 and cup 31. With the plunger in the datum position, the poison in chute 32 flows into the space vertically'between the bottom surface of metering member 17 and the top surface 15A of the metering member 15, and between rod 16 and the inner peripheral wall of tubular metering member 32. With the lock lever 49A extended into Groove Sll, the tool is taken out into the area where pocket gopher runways are located and the lower end portion is pushed in the ground, and retracted and reinserted until one feels the end portion going to the runway 60. It should be noted that .as retraction pressure is applied to the handle, the entire tool is retracted due to lock lever leg 49A extending into groove 51. Once it is felt that the lower portion of the probe has gone into a gopher runway, with the lock lever still in the locking position, retracting force is applied to the handle to move the lower end of the probe upwardly into the top part of the runway. Now the lock lever 49 is moved by the thumb of one hand to pivot in the direction opposite the arrow 53 to move the leg 49A out of the groove 51 and a retracting force is applied to the handle. Normally, due to the friction between the barrel and the ground, the barrel now will be retained in a fixed position relative to the ground while the point is retracted relative thereto. However, if necessary, one hand can be used for holding the barrel and the other for pulling on the handle.

As the plunger is retracted relative to the barrel, meter portion A moves upwardly in tubular member 33 to move the poison in the tubular member in an upward direction. As a meter member 17 moves above the upper edge of tubular member 33, the poison that was in member 33 spills over the upper edge and then falls under gravity flow through the structural free space between the tubular member and wall 11A, next downwardly through the barrel to pass between the plug and the adjacent portion of wall 11C, and thereafter outwardly through the discharge end of the barrel into the runway 60. As the meter member 15 moves continually upwardly, a continuously greater part of the discharge opening of the chute into the tubular member 33 is blocked to prevent additional poison falling into the member 33 while the poison that was in member 33 is continuously moved up over the upper edge of said member. Prior to the time the spring 45 is fully compressed, the lowermost part of surface 15A is above the upper edge of the tubular member 33, whereby the metered dose of poison has flown downwardly to pass through the discharge end of the barrel and-into the runway 60. Additionally, as meter portion 15A moves upwardly, the plug is retracted into the barrel to be spaced axially inwardly of frusto-conical portion 11D to permit the poison dropping past the plug and through the opening defined by edge 11E.

Upon the spring 25 being fully or nearly fully compressed, a further retracting force on the handle pulls the barrel out of the ground and then the resilient action of spring 25 acting against the bottom member 19 forces the barrel and mounting member to move toward the handle. As the plug moves toward edge 1 IE, it forces any material in its path of movement relative the barrel out of the barrel. As the cam surface 19A of the mounting member moves into abutting engagement with leg 49A, the locking lever is cammed out of the way until leg 49A is adjacent groove 51 whereupon spring 52 forces the leg 49A into the groove. As a result the plunger is locked in a datum position relative to the barrel.

At the time the barrel moves upwardly relative the plunger, the upper surface portion of meter member 15 moves downwardly relative the tubular member 33 to open the chute discharge opening and thereby permits the flow of poison into the chamber between member 33 and rod 16. in the plunger datum position, meter member 17 blocks the upper end of the tubular member 33 to prevent flow of poison out of the upper end of the tubular member while the upper end portion of meter member 15 extends sufficiently into the lower portion of the member 33 to prevent or block the flow of granular, grain or similar type poison through that end of the tubular member.

It is to be understood that rod portions 14, 16 and 18 may be integrally joined to one another with members 15 and 17 being annular and mounted in fixed positions on the integrally formed rod.

1 claim:

1. A poison probe comprising an elongated barrel having a lower discharge end portion, an intermediate portion and an upper end portion, said lower end portion being of a substantially smaller, transverse inner cross-sectional area than that of each of the intermediate portion and upper end portion, a plunger extending within the barrel and movable relative thereto between a datum position and a retracted position within the barrel, first means attaching the plunger to the upper end portion of the barrel for movement relative the barrel between said datum and retracted positions, said plunger having a lower plug portion that extends outwardly of the barrel and closes the lower end portion when the plunger is in its datum position and in the plunger retracted position is completely within the barrel to permit passage of poison within the barrel from the intermediate portion to and through the lower end portion between the plug and lower end portion when the plunger is in its retracted position, and second means mounted by the intermediate portion and cooperating with the plunger in the datum position for containing poison in substantially spaced relationship to said lower end portion and plug, and discharging a metered dose of said poison to fall through the barrel to the lower end portion upon moving the plunger from its datum position to its retracted position, said plunger having a first transversely enlarged portion cooperating with the second means for blocking discharge of poison in the barrel to flow downwardly to the lower end portion when the plunger is in its datum position, and moving a metered dose of poison upwardly out of the second means to discharge a metered dose of poison in the barrel to fall through the barrel to the lower end portion when the plunger is moved to its retracted position, said enlarged diametric portion being substantially spaced from the plug.

2. The apparatus of claim 1 further characterized in that plunger has a second transversely enlarged portion substantially spaced from and above the first portion and a rod portion of a smaller maximum transverse cross section area than each of said first and second portions for joining the first portion to the second portions, said first, second and rod portions being located adjacent the second means when the plunger is in its datum position, and that the second means includes third means cooperating with said first, second and rod portions when the plunger is in its datum position to form a metering chamber, said third means having a wall portion within the barrel and transversely spaced from the barrel intermediate portion to provide a passageway to permit passage of poison in the barrel from above to below the third means.

3. The apparatus of claim 2 further characterized in that the third means has an upper terminal edge that is above the lowermost part of the second portion when the plunger is in its datum position and that is located at least in part at a lower elevation than the first portion when the plunger is in its retracted position.

4. The apparatus of claim 2 further characterized in that second means includes a receptacle exterior of the housing for containing poison, said housing having a discharge opening adjacent the bottom thereof, and fourth means for mounting the receptacle on the barrel and conducting poison under gravity flow from the discharge opening to said chamber, the fourth means extending transversely into the barrel and mounting the third means.

5. The apparatus of claim 4 further characterized in that the first portion has a diagonally inclined surface, that the fourth means includes an inclined bottom wall portion forming a passageway that opens to said chamber above the first portion surface when the plunger is in its datum position.

6. The apparatus of claim further characterized in that there is provided spring means bearing against the first means and the plunger for constantly resiliently urging the plunger to its datum position, that the plunger includes handle means exterior of the barrel lock means mounted by the handle to cooperate with the first means for releasably locking the plunger in its datum position and being movable between a locking position and a nonlocking position, and spring means on the handle for resiliently urging the lock means to its locking position.

7. A poison probe comprising an elongated barrel having a lower discharge end portion, an intermediate portion and an upper end portion, said lower end portion being of a substantially smaller, transverse inner cross-sectional area than that of each of the intermediate portion and upper end portion, a plunger extending within the barrel and movable relative thereto between a datum position and a retracted position within the barrel, first means attaching the plunger to the upper end portion of the barrel for movement relative the barrel between said datum and retracted positions, said plunger having a lower plug portion to close the lower end portion when the plunger is in its datum position, said plug being located entirely within the barrel to permit passage of poison within the barrel from the intermediate portion to and through the lower end portion when the plunger is in its retracted position, a first enlarged diametric portion substantially above the plug, a rod portion joined to the first diametric portion to extend thereabove and being of a substantially smaller diameter than the said first diametric portion, a receptacle exterior of the barrel for containing a supply of poison, said receptacle having a lower discharge opening,

second means for mounting the receptacle on the barrel and extending through the barrel intermediate portion for conducting poison under gravity flow from the discharge opening to a location adjacent the plunger first portion and thereabove when the plunger is in its datum position, said second means. including third means located within the barrel for cooperating with the plunger first portion to dispense a charge of poison, permit the dispensed charge to descend under gravity flow through the barrel and thereout of as the plunger is moved from its datum position to its retracted position and block flow of poison from the receptacle to a location above said first portion when the plunger is in its retracted position.

8. The apparatus of claim 7 further characterized in that the third means includes a generally vertical tubular member having the plunger slidably extended therethrough and an axially intermediate poison inlet opening and that the second means includes fourth means forming an inclined passageway extending from the receptacle to the inlet opening to conduct poison from the receptacle to the interior of the tubular member.

9. The apparatus of claim 8 further characterized in that the plunger includes a second enlarged diametric portion above the first portion and a third portion joining the first and second portions, said first, second and third portions in the plunger datum position cooperating with the tubular member to form a metering chamher and said first and second portions in the plunger datum position acting in cooperation with the upper and end portions to close the top and bottom opening respectively of the tubular member, the second portion in the plunger retracted position being above and axially spaced from the tubular member.

$33 3 s1" TES PATENT OFFICE CERTEFICATE CF CORRECTEON Patent No. 3 77l ,474 Dated November 13, 1973 Inventor s Rue R. Elston It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 49 "ivntion" should be--invention--.

Column 3, line 36 "slidabe" should be--slidable--. Column 4,

line 7 chance" should be--free--; Column 4, line 8, "change" should be--chance--.

Signed and sealed this 2nd day of April 197M.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attestiug Officer Commissioner of Patents 

1. A poison probe comprising an elongated barrel having a lower discharge end portion, an intermediate portion and an upper end portion, said lower end portion being of a substantially smaller, transverse inner cross-sectional area than that of each of the intermediate portion and upper end portion, a plunger extending within the barrel and movable relative thereto between a datum position and a retracted position within the barrel, first means attaching the plunger to the upper end portion of the barrel for movement relative the barrel between said datum and retracted positions, said plunger having a lower plug portion that extends outwardly of the barrel and closes the lower end portion when the plunger is in its datum position and in the plunger retracted position is completely within the barrel to permit passage of poison within the barrel from the intermediate portion to and through the lower end portion between the plug and lower end portion wheN the plunger is in its retracted position, and second means mounted by the intermediate portion and cooperating with the plunger in the datum position for containing poison in substantially spaced relationship to said lower end portion and plug, and discharging a metered dose of said poison to fall through the barrel to the lower end portion upon moving the plunger from its datum position to its retracted position, said plunger having a first transversely enlarged portion cooperating with the second means for blocking discharge of poison in the barrel to flow downwardly to the lower end portion when the plunger is in its datum position, and moving a metered dose of poison upwardly out of the second means to discharge a metered dose of poison in the barrel to fall through the barrel to the lower end portion when the plunger is moved to its retracted position, said enlarged diametric portion being substantially spaced from the plug.
 2. The apparatus of claim 1 further characterized in that plunger has a second transversely enlarged portion substantially spaced from and above the first portion and a rod portion of a smaller maximum transverse cross section area than each of said first and second portions for joining the first portion to the second portions, said first, second and rod portions being located adjacent the second means when the plunger is in its datum position, and that the second means includes third means cooperating with said first, second and rod portions when the plunger is in its datum position to form a metering chamber, said third means having a wall portion within the barrel and transversely spaced from the barrel intermediate portion to provide a passageway to permit passage of poison in the barrel from above to below the third means.
 3. The apparatus of claim 2 further characterized in that the third means has an upper terminal edge that is above the lowermost part of the second portion when the plunger is in its datum position and that is located at least in part at a lower elevation than the first portion when the plunger is in its retracted position.
 4. The apparatus of claim 2 further characterized in that second means includes a receptacle exterior of the housing for containing poison, said housing having a discharge opening adjacent the bottom thereof, and fourth means for mounting the receptacle on the barrel and conducting poison under gravity flow from the discharge opening to said chamber, the fourth means extending transversely into the barrel and mounting the third means.
 5. The apparatus of claim 4 further characterized in that the first portion has a diagonally inclined surface, that the fourth means includes an inclined bottom wall portion forming a passageway that opens to said chamber above the first portion surface when the plunger is in its datum position.
 6. The apparatus of claim 5 further characterized in that there is provided spring means bearing against the first means and the plunger for constantly resiliently urging the plunger to its datum position, that the plunger includes handle means exterior of the barrel lock means mounted by the handle to cooperate with the first means for releasably locking the plunger in its datum position and being movable between a locking position and a nonlocking position, and spring means on the handle for resiliently urging the lock means to its locking position.
 7. A poison probe comprising an elongated barrel having a lower discharge end portion, an intermediate portion and an upper end portion, said lower end portion being of a substantially smaller, transverse inner cross-sectional area than that of each of the intermediate portion and upper end portion, a plunger extending within the barrel and movable relative thereto between a datum position and a retracted position within the barrel, first means attaching the plunger to the upper end portion of the barrel for movement relative the barrel between said datum and retracted positions, said plunger having a lower plug portion to cLose the lower end portion when the plunger is in its datum position, said plug being located entirely within the barrel to permit passage of poison within the barrel from the intermediate portion to and through the lower end portion when the plunger is in its retracted position, a first enlarged diametric portion substantially above the plug, a rod portion joined to the first diametric portion to extend thereabove and being of a substantially smaller diameter than the said first diametric portion, a receptacle exterior of the barrel for containing a supply of poison, said receptacle having a lower discharge opening, second means for mounting the receptacle on the barrel and extending through the barrel intermediate portion for conducting poison under gravity flow from the discharge opening to a location adjacent the plunger first portion and thereabove when the plunger is in its datum position, said second means including third means located within the barrel for cooperating with the plunger first portion to dispense a charge of poison, permit the dispensed charge to descend under gravity flow through the barrel and thereout of as the plunger is moved from its datum position to its retracted position and block flow of poison from the receptacle to a location above said first portion when the plunger is in its retracted position.
 8. The apparatus of claim 7 further characterized in that the third means includes a generally vertical tubular member having the plunger slidably extended therethrough and an axially intermediate poison inlet opening and that the second means includes fourth means forming an inclined passageway extending from the receptacle to the inlet opening to conduct poison from the receptacle to the interior of the tubular member.
 9. The apparatus of claim 8 further characterized in that the plunger includes a second enlarged diametric portion above the first portion and a third portion joining the first and second portions, said first, second and third portions in the plunger datum position cooperating with the tubular member to form a metering chamber and said first and second portions in the plunger datum position acting in cooperation with the upper and end portions to close the top and bottom opening respectively of the tubular member, the second portion in the plunger retracted position being above and axially spaced from the tubular member. 